JPH11121220A - Low loss dust core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance reliability by providing the constitution, which comprises the mixed powder of solft magnetic metal material and permanent magnetic material, has a structure of which an S-pole at one end of the cross section perpendicular to a magnetic path and an N-pole at the opposite pole of the S pole. SOLUTION: A compressed dust body comprising soft magnetic metal material and permanent magnet material 1 is magnetized in a vertical direction 3 with respect to its magnetic path direction 2. Thus, as S-pole is provided at one end of the cross section which is perpendicular to the magnetic path, and an N pole is provided at the opsite pole. The magnetic flux of the surface is set at 100-1,000 G. The reason for the surface magnetic flux being set at 100-1,000 G in the magnetizing direction is that, when the magnetic flux is smaller than 100 G, a magnetic wall is present and the loss is not decreased. Furthermore, when the value is larger than 1,000 G, the alignment of spin in the exciting direction is not easy, and the loss other than hysteresis is deteriorated. The reason why the total loss of the dust core can be decreased in this way is the fact that the hysteresis loss and the vortex loss are both decreased by mixing the permanent magnet material powder and applying the magnetic field in the direction perpendicular to the magnetic path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance dust core used for a choke coil or the like, and more particularly to a low-loss dust core.

[0002]

2. Description of the Related Art As a choke coil used at a high frequency, a soft magnetic ferrite core or a dust core manufactured by molding a soft magnetic metal material powder is used. Among them, the ferrite core has a disadvantage that the saturation magnetic flux density is small. On the other hand, the dust core has an advantage that it has an excellent DC superimposition characteristic because it has a higher saturation magnetic flux density than the ferrite core.

On the other hand, with the recent trend toward miniaturization and high frequency of electronic equipment, it is required to reduce the loss of the dust core in order to improve the stability and reliability of the dust core and its surrounding parts. Have been.

[0004] Generally, the core loss is a hysteresis loss,
It consists of eddy current loss and residual loss. Among them, the eddy current loss is reduced by a method of forming an insulating film on the surface of the alloy powder or a method of mixing an insulating binder. Further, in order to further reduce the loss, it is necessary to reduce the hysteresis loss or the residual loss.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a low-loss powder magnetic core having stable characteristics and excellent reliability in view of the above-mentioned drawbacks.

[0006]

The present invention comprises a mixed powder of a soft magnetic metal material and a permanent magnet material, and has an S pole at one end of a cross section perpendicular to the magnetic path and an N pole at a counter electrode of the S pole. It is a low loss dust core.

Further, according to the present invention, the surface magnetic flux in the magnetization direction is 1
The low-loss powder magnetic core according to the present invention is 100 to 1000 G.

In the present invention, the total loss of the dust core was reduced by mixing the permanent magnet material powder and applying a magnetic field in a direction perpendicular to the magnetic path of the dust core. This is considered to be because hysteresis loss caused by the disappearance and irreversible movement of the domain wall and eddy current loss locally generated in the crystal grain due to the domain wall movement are both reduced.

In the dust core of the present invention, the surface magnetic flux in the magnetizing direction of the permanent magnet is set to 100 to 1000 G. If the surface magnetic flux is smaller than 100 G, the domain wall in the dust core will remain and the loss will be reduced. Is not reduced. On the other hand, if it is larger than 1000 G, the orientation of spins in the excitation direction is not easy, and losses other than the hysteresis loss deteriorate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a green compact made of a mixed powder of a soft magnetic metal material and a permanent magnet material 1 is magnetized in a direction 3 perpendicular to the magnetic path direction 2, thereby obtaining A low-loss powder magnetic core which has an S-pole at one end of a cross section perpendicular to the magnetic path and an N-pole at the opposite pole thereof and has a surface magnetic flux of 100 to 1000 G, low heat generation and low heat generation is obtained.

[0011]

【Example】

(Example 1) 10 wt% Si produced by an atomizing method
Percentage of the permanent magnet material powder was 20, 40, 60, 80, 1 by volume ratio with respect to the -5 wt% Al- balance Fe alloy powder.
3 wt% of silicone resin mixed with 00, 120%
%, And using a mold having an outer diameter of 20 mm and an inner diameter of 10 mm,
It was molded at 5 ton / cm ² at room temperature to obtain a toroidal green compact.

Next, these compacts were subjected to binder curing in the atmosphere at 170 ° C. for 2 hours. Next, heat treatment was performed at 700 ° C. for 2 hours in the air which is an oxidizing atmosphere. Thereafter, magnetization was performed in a direction perpendicular to the magnetic path of the dust core.

(Comparative Example 1) 1 prepared by the atomizing method
0 wt% Si-5 wt% Al-balance Fe alloy powder mixed with 3 wt% silicone resin, outer diameter 20 mm, inner diameter 10
using a 5 mm mold at room temperature at 5 ton / cm ²
A toroidal green compact was obtained. Next, this green compact is
The binder was cured in air at 70 ° C. for 2 hours. Next, heat treatment was performed at 700 ° C. for 2 hours in the air which is an oxidizing atmosphere.

Table 1 shows that the powder magnetic core of Example 1 (in which the amount of the permanent magnet material powder to be mixed was changed and the surface magnetic flux in the magnetization direction of the powder magnetic core was changed) and the dust core of Comparative Example 1 were 200 kHz. ,
The loss (Pcv), the hysteresis loss (Ph), and the loss other than the hysteresis loss (eddy current loss and residual loss) (Pcv-Ph) at 1000 G and 30 ° C. are shown. Note that the permanent magnet material has a considerably lower magnetic permeability than the Fe-Si-Al-based alloy, so that the loss of the permanent magnet material itself can be ignored here. * In the table indicates Comparative Example 1.

[0015]

(Example 2) F produced by an atomizing method
e powder and permanent magnet material powder in a volume ratio of 2
A mixture of 0, 40, 60, 80, 100, and 120% is mixed with 3% by weight of a silicone resin, and molded at 5 ton / cm ² at room temperature using a mold having an outer diameter of 20 mm and an inner diameter of 10 mm. A powder was obtained.

Next, these green compacts were subjected to binder curing in air at 170 ° C. for 2 hours. Next, heat treatment was performed at 700 ° C. for 2 hours in the air which is an oxidizing atmosphere. Thereafter, magnetization was performed in a direction perpendicular to the magnetic path of the dust core.

(Comparative Example 2) F produced by the atomizing method
e Powder mixed with 3wt% silicone resin, outer diameter 20m
m, 5 ton / cm at room temperature using a mold with an inner diameter of 10 mm
^Then , a green compact having a toroidal shape was obtained. Next, this green compact was subjected to binder curing in the atmosphere at 170 ° C. for 2 hours. Next, in the atmosphere which is an oxidizing atmosphere, 700
C. for 2 hours.

Table 2 shows the loss (P at 200 kHz, 1000 G, and 30 ° C.) of the dust cores of Example 2 and Comparative Example 2.
cv), a hysteresis loss (Ph), and a loss other than the hysteresis loss (Pcv-Ph). Since the magnetic permeability of the permanent magnet material is considerably lower than that of Fe, the loss of the permanent magnet material itself can be ignored here. In the table, * indicates Comparative Example 2.

[0020]

Tables 1 and 2 show that Pcv is reduced when the surface magnetic flux of the dust core is in the range of 100 to 1000 G. This is because both Ph and Pcv-Ph are reduced. Also, with a surface magnetic flux of 50G,
The loss of the Fe-Si-Al-based alloy and Fe is the same as when no permanent magnet material is mixed. In addition, the surface magnetic flux 12
At 00G, the loss is degraded for both the Fe-Si-Al-based alloy and Fe. This is because the loss other than the hysteresis loss is degraded although the hysteresis loss is reduced.

In this embodiment, examples of the Fe--Si--Al alloy and Fe are shown. However, similar effects can be obtained with an Fe alloy such as an Fe--Ni--Mo alloy.

[0023]

According to the present invention, it is possible to provide a low-loss powder magnetic core having stable characteristics and excellent reliability.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a magnetic path direction and a magnetization direction of a dust core of the present invention.

[Explanation of symbols]

 1 permanent magnet material 2 magnetic path direction 3 (magnetized) direction

Claims (2)

[Claims] 1. A low loss pressure comprising a mixed powder of a soft magnetic metal material and a permanent magnet material, having an S pole at one end of a cross section perpendicular to a magnetic path and an N pole as a counter electrode of the S pole. Powder core. 2. The surface magnetic flux in the magnetization direction is 100 to 1000.
2. The low-loss powder magnetic core according to claim 1, wherein G is G.